Keying



March 20, 1934. w. BUSCHBECK KEYING Filed NOV. 8, 1930 INVENTOR WERNER BUSCHBECK BY ATTORNEY Patented Mar. 20, 1934 PATENT: QFFICE KEYING Werner Buschbeck, Berlin, Germany, assignor to Telefunken Gcsellschaft fiir Drahtlose Telegraphic 111. b. 11., Berlin, Germany, a corporation of Germany Application Claims.

In code signalling the keying of the signals in one of the transmitter tubes is often accomplished by controlling at keying speed the direct current potential applied to the grid electrode 5 of a tube or tubes in the transmitter through which high frequency oscillations are relayed or repeated. For spacing the radio frequency plate current is suppressed in the keying tube by sufficiently high negative grid biasing potential,

while for marking or signalling the said biasing potential is removed so that the tube is subjected to complete modulation. When a tube is keyed in this manner, the plate current is subject to sudden and marked fluctuations, that is, from zero to crest value. This, on the one hand, means an undue load and stress on the rectifiers, plate-current generators, etc., while on the other hand, owing to the inductance of the circuits the speed of telegraphy keying is reduced.

This condition may be remedied by feeding the plate direct current during spaces to the plate circuit of another tube connected with the same plate current source, so that the current derived from the rectifiers or generators remains con- 'stant in value. This is what may be called a load-balancing tube and in operation this auxiliary tube is blocked while signal markings are produced in the plate circuit of the keying tube so that it will not take any plate current during 1 such periods. According to the present invention, the said blocking is accomplished by connecting the plate current of the keyed stage, or one of the stages higher up, with the filament by way of a resistance. The plate current fiowing through this resistance while the transmitter is operative results in a fall of potential across the resistance which serves directly, or else after suitable amplification, for the blocking of the absorber tube.

The principle underlying the present invention will be explained hereinafter by the aid of the accompanying drawing which, it is to be clearly understood is only illustrative and not limitative of the present invention.

Referring to the drawing, the manipulator or 1 key 1 is inserted in the grid circuit of the keying tube 2 which is supplied with plate current from the source of potential 3. The resistance 4 is provided in the plate circuit of this tube in accordance with the basic idea of this invention. The grid of the absorber tube 5 is connected to a terminal of resistance 4. The plate 6 of tube 5 is connected through a resistance 8 to the positive terminal of the rectifier, while the filament 7 of tube 5 is connected to the negative terminal of the rectifier. The plate 10 of the tube 11 of the trans- November 8, 1930, Serial No. 494,271 Germany November 26, 1929 mitter power stage is also connected through a choke coil 12 to the positive terminal of the rectifier while the filament 13 of tube 11 is connected to the negative terminal of the rectifier. Direct current potential is therefore supplied for both tubes 5 and 11 from the single source which has been shown, by way of example, as a rectifier.

In operation when key 1 is closed tube 2 becomes conductive and current flows in the plate 5' circuit of tube 2. This results in the energizing of the grid electrode of tube 11 so that a pulse of high frequency oscillations is sent out. The frequency of these oscillations is determined by the frequency of the oscillations applied to the input circuit of tube 2. Direct current is now flowing through resistance 4 in the plate and filament circuit of tube 2. The plate current flowing through resistance 4 when the key is depressed occasions a fall of potential across the same whereby the absorber tube is blocked so that tube 5 draws no plate current. When the key ,1 is opened tube 2 becomes nonconductive and the oscillations impressed on the input circuit thereof are not amplified. These oscillations theregm fore are not repeated in 2 and do not appear on the input circuit of the transmitter power stage tube 11. The impulse or marking signal, being sent out, is terminated so that a space or interval appears in the signal. Since tube 2 is noncong5} ductive the current flowing in the plate filament circuit including resistance 4 drops and negative potential is removed from the grid of absorber tube 5. Tube 5 now becomes conductive so that direct current flows in the plate filament circuit thereof. In this manner tubes 5 and 11 are alternately conductive and nonconductive so that a constant direct current load is placed on the rectifier at all times.

I claim:

1. In apparatus of the character described, a power tube having input and output electrodes, a load circuit connected between the output electrodes, a keying tube, a source of high frequency oscillations and a key connected in parallel with 1'01) the input electrodes thereof, an alternating current circuit connected between the output electrodes of said keying tube, a connection between said last named circuit and the input electrodes of said power amplifier, a source of potential 1'65 and a resistance connected in series with the output electrodes of said keying tube, an absorber tube, means for connecting the anode cathode circuit of said absorber tube in parallel with the anode cathode circuit of said power amplifier and ,of said absorber in parallel with a direct current source, and a connection between the resistance in the output circuit of said keying tube and the control grid in said absorber tube.

2. In apparatusof the character described, a thermionic repeater tube having anode, cathode and control grid electrodes, an alternating current output circuit connected between said anode and said cathode, a keying tube having anode,

cathode and control electrodes, a source of high frequency oscillations connected between the con trol electrode and cathode ofpsaid keying tube, a key connected in parallel with said source, an alternating current circuit connected between the anode and cathode of said tube, a connection between the anode of said keying tube and the control grid electrode of said first named tube,

a direct current source and a resistance connected between the anode and cathode-of said keying tube, a source of direct current connected between the anode and cathode of said first named tube, and means for maintaining a constant'drain'on said last named source during keying and non-keying operations of said keying tube comprising, an absorber tube having an" anode, cathode and control grid electrode, means for connectingthe anode to cathode impedance tube in parallel with said last named direct current source, and aconnection between the control grid of said, absorber tube and the terminal'of said resistance adjacent said first named direct current source.

- 3. In apparatus of'the character described, a power tube, a source of carrier frequency osci1- i lations, a keying tube having its input electrodes coupled to said source of carrier frequencyioscib lations and its output electrodes coupled to said power tube input for controlling the output thereof, a' key connected with said keying tube, an absorber tube connected inparallel with the power tube, and a resistance in the output circuit of the keying tube,,said resistance being coupled to an electrode in the absorber tube in a fashion such that the absorber tube is rendered conductive as the power tube is rendered non-conductive, and vice versa.

4. In apparatus of the character described, a power tube, a keying tube having a source of carrier frequency oscillations and keying means connected with its input electrodes and a circuit between its output electrodes and the input of said power tube for applying keyed oscillations and control electrodes, a source of energizing potential connected between the anode and cath-" ode, a work circuit connected with the anode of said tube, a source of carrier frequency oscillations, a keying'tube having anode, cathode andcontrol electrodes, keying means connected between said source of carrier frequency oscillations and the control electrode of said keying;

tube, a connection between the anode of said keying tube and the control electrode of said amplifier tube so that the amplifier tube is con-i trolled by said keying tube, an energizing, circuit including a source of, potentialand an impedanceconnected between'the anode and cathode of saidv keying tube, an absorption tube of they triode type, a circuit for connecting the anode'to oath-r ode impedance of said absorption tube with said source of potential connected with the anode of:

said amplifier tube, and a circuit connecting the control grid of said absorption tube'to a point on said impedance.

WERNER BUSCHBECK. 

